Genetic Inheritance and Genetic Data

Eric C. Anderson

The Wildlife Society CKMR Workshop, Sunday November 6, 2022

Outline

  1. Motivation
  2. Mendelian Inheritance
  3. Identity-by-descent
  4. Physical linkage
  5. Genetic markers and identity in state
  6. Pairwise joint genotype probabilities
  7. Types of genetic markers

Motivation

Starting from the beginning

  • Gregor Mendel (1822-1884)
  • Inferred laws of genetic segregation by observing patterns of single-locus traits in pea plants.
  • Not applicable to most (polygenic) traits
  • But, we now know his laws are quite applicable to the transmission of genetic material in diploid organisms.
  • They apply to dicussing the inheritance of a locus.

What the heck is a locus?

  • The word “locus” in genetics, much like the word “gene” has been applied to a lot of things.

  • For our purposes, we will use it to refer to a “chunk” of DNA that is defined by its position in the genome.

  • For example, around base position X on Chromosome 3:

  • Two copies of the DNA at each locus. One chromosome from mom. Another from dad.

Mendels Law of Segregation

When gametes are formed, the two copies of each locus segregate so that each gamete carries exactly one copy of each locus.

Since individuals are formed by the union of gametes, this dictates the segregation of DNA to offspring.